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10.6 Fertilization Program for Established Orchards

Leaf analysis indicates the concentration of nutrients that are present in the foliage. If leaf samples are taken correctly and the results are interpreted properly, it provides a good tool for developing an effective fertilization program. Leaf analysis standard for fruit trees are listed in Table 10.6.1.

Leaf samples should be collected between 60 to 70 days after petal fall, which generally corresponds to late July and early August. Mid-shoot leaves should be sampled from current season terminal shoots on the periphery of the tree. Sample trees should represent the general conditions of the orchard in terms of vigor, crop load, etc. Each sample should consist of about 100 leaves collected from several trees in the area being sampled. Do not mix leaves from different varieties, soil conditions, tree vigor, or crop load. Record observations on terminal shoot length, thickness, crop load, and fruit size. Leaf samples can be sent to: Cornell Nutrient Analysis Lab, 804 Bradfield Hall, Cornell University, Ithaca, NY 14853, Phone 607-255-4540, Fax 607-255-7656.

It should be recognized that leaf analysis has its limitations. First, leaf samples are taken relatively late in the growing season. Even if you can get the leaf analysis results back immediately, you may not have enough time left during the season to correct mineral deficiencies if there are any. Secondly, routine leaf analysis cannot detect the transient nutrient demand by certain physiological processes early in the season. For example, trees have a large transient demand for boron at bloom. Finally, even if leaf analysis shows no mineral nutrient deficiency, you still need to have a maintenance program in place to replace the amount of nutrients that is lost in harvested fruit and fallen leaves every year. Therefore, two fertilization programs are suggested here for established trees. One is a maintenance program. The other is a corrective program for trees with nutrient deficiency.

Table 10.6.1. Leaf analysis standards for tree fruits (dry weight basis).

Element

Crop

Desired level

Nitrogen

Young nonbearing apples and pears

Young bearing apples and pears

Mature soft apples and pears

Mature hard apples and processing

Cherries, plums, prunes

Peaches

2.4-2.6%

2.2-2.4%

1.8-2.2%

2.2-2.4%

2.4-3.4%

3.0-4.0%

Phosphorus

Potassium

Calcium

Magnesium

All crops

Apples and pears

Stone fruits

0.13-0.33%

1.35-1.85%

1.3-2.0%

0.35-0.50%

0.40-0.60%

Boron

Zinc

Copper

Manganese

Iron

Apples and pears

Stone fruits

All crops

35-50 ppm

30-40 ppm

30-50 ppm

7-12 ppm

50-150 ppm

50+ ppm

10.6.1. Maintenance program

This program is suggested when leaf analysis shows no nutrient deficiency or no deficiency symptoms are observed.

Timing	Foliar Sprays	Ground Applications
Green tip	One spray of 2 to 4 lbs of a fixed copper product per 100 gal (C-O-C-S or Kocide).
Tight cluster to pink	One spray of tank mixed 3 lbs of urea and 1 lb Solubor/100 gal	Apply 20 to 40 lbs of actual nitrogen/acre to soil.
Petal fall to early cover sprays	One spray of Zn-EDTA at label rate at second cover. Plus One spray of 3 to 4 lb of calcium chloride/100 gal at third cover. Plus Two sprays of 10-15 lb of Epsom salt/100 gal at petal fall, and second cover.	Apply 40 to 60 lbs of potassium/acre to soil at petal fall.
End of shoot growth to harvest	Three to four sprays of 3 to 4 lbs of calcium chloride/100 gal at 14-day intervals for bitter pit susceptible varieties.
After harvest		Apply 40 to 60 lb of potassium/acre to soil. Plus Every 2 to 3 years, apply appropriate amount of lime determined from soil analysis.

10.6.2 Corrective program

This program is suggested when leaf analysis shows nutrient deficiency, or deficiency symptoms are observed. Match fertilizer applications to specific nutrient deficiency.

Timing	Foliar Sprays	Ground Applications
Green tip	One spray of 2 to 4 lbs of a fixed copper product per 100 gal (C-O-C-S or Kocide)
Prebloom period	Two sprays of tank-mixed 1 lb of Solubor, 3 lbs of urea, and Zn-EDTA at label rate per 100 gallon, one at 1/2" green and the other at tight cluster to pink	Apply 40 to 60 lbs of actual nitrogen/acre to soil.
Petal fall to early cover sprays	Two foliar sprays of 5 lbs of urea/100 gal at petal fall and first cover. Plus Two sprays of Zn-EDTA at label rate at petal fall and second cover. Plus Two foliar sprays of 1 lb of Solubor/100 gal at first and third cover. Plus Three sprays of 10-15 lbs of Epsom salt/100 gal applied at petal fall, first and second covers. Plus One foliar spray of 3 to 4 lbs of calcium chloride per 100 gal at third cover.	Apply 60 to 150 lbs of Potassium/acre to soil at petal fall.
End of shoot growth to harvest	Five to six sprays of 3 to 4 lbs of calcium chloride/100 gal at 14-day intervals.	Apply 60 to 150 lbs of potassium to soil at the end of shoot growth.
After harvest	Two sprays of 25 lbs of urea/100 gal at 7 to 10-day intervals. Plus One spray of 1 lb of actual copper/acre as copper sulfate.	Soil application of 60 to 150 lbs of potassium/acre as sulfate of potash-magnesia. Plus Soil application of dolomitic lime to increase calcium and magnesium supply based on soil and leaf analyses.

10.6.4 Special Considerations in Foliar Application of Nutrients

To minimize the number of sprays applied in the orchard, it is frequently desirable to combine various nutrient materials or to add them in tank mixes with pesticides. Before doing so, however, one needs to make sure they are compatible.

Generally, urea, Solubor, and Zn-EDTA are compatible. Urea, Solubor, and Zn-EDTA have been used together safely in prebloom sprays on apples and pears. A tank mix of urea and Epsom salts has sometimes injured young apple foliage; if both are required, they should be applied separately. Epsom salts and some of the boron products listed in Table 10.6.5 may increase the pH of the tank mix, and if used with pH-sensitive pesticides, pH of the tank mix should be tested and adjusted by using a suitable acidifying agent. Solubor and presumably other forms of boron should not be tank-mixed with any pesticide contained in water-soluble plastic packages because it inhibits the dissolution of the plastic. In general foliar nutrients should not be mixed with oil. Solubor in particular should not be tank-mixed with oil.

Although Epsom salts, Solubor and Zn-EDTA are compatible for use in postbloom sprays, many orchardists prefer not to add all three to one tank. A petal fall spray may then contain Epsom salts alone or with Solubor; the first cover spray a combination of Epsom salts and Solubor; the second cover spray a combination of Epsom salts and Zn-EDTA; and the third cover spray a combination of Solubor and Zn-EDTA.

Calcium chloride may be physically incompatible with Epsom salts, resulting in plugging of sprayer nozzles. Calcium chloride cannot be tank-mixed with Zn-EDTA because some of the dissolved calcium may displace Zn, causing phytotoxicity.

It should be pointed out that some Zn-chelate products contain a large percentage of unchelated Zn, which may cause injury to foliage and fruit. Therefore, before using a new Zn product in your orchard, test the product by spraying a few trees at the label rate to see if any phytotoxicity occurs.

More detailed information concerning nutrient management for orchards can be found in Cornell Cooperative Extension Information Bulletin 219, Orchard Nutrition Management by Warren Stiles and Shaw Reid. See the section on “Tree Fruit Reference Materials” at the end of this publication for ordering information.

Prepared by Lailiang Cheng, Dept. of Horticulture, Ithaca, and Terence Robinson, Dept. of Horticultural Sciences, Geneva.

10.6.5 Characteristics of Commonly Available Fertilizers

Table 10.6.2. Nitrogen fertilizers
Common name	% N	Pounds per lb N	Acidity or Basicity (lb CaCO₃/lb
Common name	% N	Pounds per lb N	*Acidity*	*Basicity*
Ammonia, anhydrous	82	1.22	1.8	—
Ammonia, aqua	20	5.00	1.8	—
Ammonium nitrate	33.5	2.98	1.8	—
Ammonium polyphosphate	12	8.33	4.1	—
Ammonium sulfate	20.5	4.88	5.4	—
Calcium nitrate	15.5	6.45	—	1.3
Diammonium phosphate	16-18	5.56	4.1	—
Monoammonium phosphate	11	9.09	5.3	—
Nitrate of soda-potash	15.5	6.45	—	1.3
Potassium nitrate	13	7.69	—	2.0
Sodium nitrate	16	6.25	—	1.8
Urea	45	2.22	1.6	—
Nitrogen solutions	variable¹	—	—	—
¹Nitrogen solutions may consist of mixtures of urea plus ammonium nitrate, aqua ammonia, or anhydrous ammonia plus urea or ammonium nitrate or both of these materi als. Consult supplier for analysis.

Table 10.6.3. Phosphorus fertilizers
Common name	P₂O₅(%)	Pounds per lb P₂O₅	N (%)
Ordinary superphosphate	20	5	0
Concentrated superphosphate	46	2.27-2.17	0
Ammoniated superphosphate	40*	2.5*	5*
Monoammonium phosphate	52*	1.92*	13*
Diammonium phosphate	46*	2.17*	18*
Urea-ammonium phosphate	28	3.57	28
*Values may vary depending on fertilizer source.

Table 10.6.4. Potassium fertilizers
Common name	Chemical Formula	% K₂O	Pounds of Formulated Product per Lb. of K₂O
Muriate of Potash	KCl	60	1.67
Sulfate of Potash	K2SO4	53	1.89
Sulfate of Potash Magnesia	K₂SO₄•2MgSO₄	22	4.54
Potassium polyphosphate	KPO₃	40	2.50
Potassium carbonate	K₂CO₃	67	1.50
Potassium nitrate	KNO₃	44	2.27

Table 10.6.5. Boron fertilizers¹
Product Name	%B (W/W)	Form of B*	Increase in spray water pH	Cost per lb. B
B-17	17.0	BA	none	low
Mor-Bor 17	17.3	BA	none	low
Spray-Bor	16.5	NaB	moderate	low
Solubor	20.5	NaB	high	very low
Solubor DF	17.4	NaB	high	n/a
Albion Liquid B	5.0	NaB	high	high
Liquibor	2.5	BA, NaB	high	high
Borosol 10	10.0	BA	very high	moderate
N-Boron	5.4	BA	very high	n/a
^Form of boron indicates boron compound used in formulating the product: BA:* boric acid; NaB: sodium polyborates. ¹From Dr. Frank Peryea, Washington State University.

Table 10.6.6. Miscellaneous fertilizers
Name	Mineral element	Content (%)
Gypsum	Ca	24
Superphosphate	Ca	20
Concentrated superphosphate	Ca	14
Calcium nitrate	Ca	24
Calcium chloride (77-80%)	Ca	27.8
Calcium chloride(35% liquid)	Ca	12.6
Calcium chelates	Ca	variable
Epsom salts	Mg	10
Kieserite	Mg	17.3
Magnesium oxide	Mg	49-56
Magnesium sulfate	Mg	16
Zinc chelate	Zn	Variable
Zinc sulfate	Zn	36%
Basic zinc sulfate	Zn	50-52
Copper chelate	Cu	Variable
Copper sulfate	Cu	25%

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